Pancratic wide-angle objective

ABSTRACT

A pancratic wide-angle objective comprises a stationary negative front component in the form of a single meniscus with a convex forward surface, an axially movable intermediate component consisting of a biconvex lens, and a stationary multilens positive rear component separated from the front component by an airspace greater than the focal length of the latter. The individual focal lengths of the front, intermediate and rear components have absolute values in a ratio of approximately 4:5:3.

BACKGROUND OF THE INVENTION

The invention relates to a powerful pancratic wide angle projection objective of the type described in Swiss Pat. No. 522,230. This patent describes an objective with a negative front component and a positive rear component between which, for the variation of the focal length, a further positive lens member is axially movable. The shortest focal length of this objective is a multiple of the diagonal of the image to be projected.

OBJECTS OF THE INVENTION

It is a primary object of the invention to provide an optical system adapted to focus an objective of the width of the Super-8 format within short distances such as 250 - 500 mm onto an image screen.

It is a further object of the invention to provide an optical system for projecting a Super-8 image frame within a distance of about 500 mm, with a 300-mm image width.

SUMMARY OF THE INVENTION

We have found, in accordance with the present invention, that the foregoing objects can be realized by designing the negative front component as a meniscus-shaped lens member with a concave surface turned toward the intermediate component and with an absolute focal length greater than that of the rear component but less than that of the intermediate component. The airspace separating the front and rear components advantageously exceeds the focal length of the front component and equals approximately twice the focal length of the rear component. A pronounced wide-angle effect results from this construction; the minimum overall focal length is shorter than or, at most, equal to the image diagonal 2y'.

BRIEF DESCRIPTION OF THE DRAWING

The above and other features of our invention will be described in greater detail with reference to the accompanying drawing the sole FIGURE of which schematically illustrates an objective according to our invention in a position of intermediate overall focal length f_(M).

SPECIFIC DESCRIPTION

The objective shown in the drawing consists of three distinct components, namely a negative front component GI, an axially movable positive intermediate component GII and a stationary positive rear component GIII. Component GI, positioned on the side of the longer conjugate intercept distance normally referred to as the object side, is a single lens L₁ of thickness d₁ and radii r₁, r₂ in the form of a negative meniscus with a convex forward surface. A variable airspace l₁ separates this lens from a biconvex lens L₂ constituting the positive intermediate component, lens L₂ having a thickness d₂ and radii r₃, r₄. Another variable airspace l₂, considerably smaller than airspace l₁ in all operating positions of the objective, intervenes between lens L₂ and a positive first lens L₃ (thickness d₃ and radii r₅, r₆) of rear component GIII; the other members of this component are a positive second lens L₄ (thickness d₄ and radii r₇, r₈), a negative third lens L₅ (thickness d₅ and radii r₉, r₁₀) and a positive fourth lens L₆ (thickness d₆ and radii r₁₁, r₁₂). The lens L₃ - L₆ are separated by airspaces l₃, l₄ and l₅. Lens L₆ lies closest to a film whose frames are to be projected upon a nonillustrated screen on the object side.

Representative numerical values for the radii r₁ - r₁₂, the thicknesses d₁ - d₆ and the separations l₁ - l₅, based on a numerical value of unity for the minimum overall focal length f_(min), are given for three Examples in the following Tables, together with the refractive indices n_(d) and Abbe numbers v_(d).

EXAMPLE I

                               n.sub.d                                                                               v.sub.d                                        r.sub.1                                                                            + 7.072                                                                  L.sub.1      d.sub.1                                                                            0.229     1.658                                                                               / 50.9                                           r.sub.2                                                                            + 1.972                                                                                   5.530     f.sub.min                                                        L.sub.1                                                                            5.102     f.sub.M                                                              4.516     f.sub.max                                             r.sub.3                                                                            + 8.596                                                                  L.sub.2      d.sub.2                                                                            0.457     1.589                                                                               / 61.3                                           r.sub.4                                                                            - 4.856                                                                                   0.014     f.sub.min                                                        1.sub.2                                                                            0.443     f.sub.M                                                              1.029     f.sub.max                                             r.sub.5                                                                            + 2.137                                                                  L.sub.3      d.sub.3                                                                            0.372     1.589                                                                               / 61.3                                           r.sub.6                                                                            + 14.894                                                                              1.sub.3                                                                            0.014                                                           r.sub.7                                                                            + 1.425                                                                  L.sub.4      d.sub.4                                                                            0.500     1.589                                                                               / 61.3                                           r.sub.8                                                                              ∞                                                                             1.sub.4                                                                            0.104                                                           r.sub.9                                                                            - 5.597                                                                  L.sub.5      d.sub. 5                                                                           0.643     1.785                                                                               / 25.8                                           r.sub.10                                                                           + 0.768                                                                               1.sub.5                                                                            0.121                                                           r.sub.11                                                                           + 4.705                                                                  L.sub.6      d.sub.6                                                                            0.286     1.691                                                                               / 54.7                                           r.sub.12                                                                           - 1.364                                                                               f.sub.min                                                                               1.000                                                                 f.sub.M  1.087                                                                 f.sub.max                                                                               1.216                                                                 2.sub.y '                                                                               1.000                                                                 aperture ratio                                                                          1:1.3                                               

EXAMPLE II

      r.sub.1                                                                            + 14.316                n.sub.d                                                                               v.sub.d                                   L.sub.1      d.sub.1                                                                            0.286        1.589                                                                               / 61.3                                        r.sub.2                                                                            + 1.960                                                                                   5.497     f.sub.min                                                        l.sub.1                                                                            5.011     f.sub.M                                                              4.524     f.sub.max                                             r.sub.3                                                                            + 5.234                                                                  L.sub.2      d.sub.2                                                                            0.458        1.589                                                                               / 61.3                                        r.sub.4                                                                            - 7.490                                                                                   0.058     f.sub.min                                                        l.sub.2                                                                            0.545     f.sub.M                                                              1.032     f.sub.max                                             r.sub.5                                                                            + 2.434                                                                  L.sub.3      d.sub.3                                                                            0.344        1.589                                                                               / 61.3                                        r.sub.6                                                                            + 33.380                                                                              l.sub.3                                                                            0.014                                                           r.sub.7                                                                            + 1.507                                                                  L.sub.4      d.sub.4                                                                            0.558        1.589                                                                               / 61.3                                        r.sub.8                                                                              ∞                                                                             l.sub.4                                                                            0.106                                                           r.sub.9                                                                            - 5.485                                                                  L.sub.5      d.sub. 5                                                                           0.573        1.785                                                                               / 26.1                                        r.sub.10                                                                           + 0.888                                                                               l.sub.5                                                                            0.129                                                           r.sub.11                                                                           + 3.800                                                                  L.sub.6      d.sub.6                                                                            0.315        1.691                                                                               / 54.7                                        r.sub.12                                                                           - 1.722                                                                               f.sub.min                                                                               1.000                                                                 f.sub.M  1.102                                                                 f.sub.max                                                                               1.217                                                                 2y'      1.000                                                                 Aperture ratio                                                                          1:1.3                                               

EXAMPLE III

      r.sub.1                                                                            + 13.048             n.sub.d                                                                               v.sub.d                                      L.sub.1      d.sub.1                                                                            0.255     1.589                                                                               / 51.4                                           r.sub.2                                                                            + 2.107                                                                                   5.452                                                                      l.sub.1                                                                            4.956                                                                          4.459                                                           r.sub.3                                                                            + 5.226                                                                  L.sub.2      d.sub.2                                                                            0.454     1.589                                                                               / 61.3                                           r.sub.4                                                                            - 7.480                                                                                   0.050                                                                      l.sub.2                                                                            0.547                                                                          1.043                                                           r.sub.5                                                                            + 2.282                                                                  L.sub.3      d.sub.3                                                                            0.369     1.589                                                                               / 61.3                                           r.sub.6                                                                            + 31.295                                                                              l.sub.3                                                                            0.014                                                           r.sub.7                                                                            + 1.412                                                                  L.sub.4      d.sub.4                                                                            0.496     1.589                                                                               / 61.3                                           r.sub.8                                                                              ∞                                                                             l.sub.4                                                                            0.099                                                           r.sub.9                                                                            - 5.555                                                                  L.sub.5      d.sub.5                                                                            0.638     1.785                                                                               / 26.1                                           r.sub.10                                                                           + 0.755                                                                               l.sub.5                                                                            0.135                                                           r.sub.11                                                                           + 3.444                                                                  L.sub.6      d.sub.6                                                                            0.284     1.691                                                                               / 54.7                                           r.sub.12                                                                           - 1.376                                                                               f.sub.min                                                                               1.000                                                                 f.sub.M  1.102                                                                 f.sub.max                                                                               1.216                                                                 2y'      1.000                                                                 Aperture ratio                                                                          1:1.3                                               

From the foregoing values the individual focal lengths f_(I), f_(II) and f_(III) of components GI, GII and GIII can be calculated as follows:

    EXAMPLE     f.sub.I    f.sub.II   f.sub.III                                    ______________________________________                                         I           -4.12      +5.35      +2.934                                       II          -3.89      +5.28      +3.025                                       III         -4.21      +5.28      +2.789                                       ______________________________________                                    

It will thus be seen that the individual focal lengths f_(I), f_(II) and f_(III) of components GI, GII, GIII have absolute values approximately in the ratio of f_(I) :f_(II) :f_(III) = 4:5:3 in all three instances. The minimum focal length f_(min) is about one-third of the individual focal length f_(III).

It will also be noted from the Tables that the range of displacement of intermediate component GII between its positions of minimum overall focal length f_(min) and maximum overall focal length f_(max) is in each case approximately equal to unity, and thus to the minimum focal length f_(min), with the first variable airspace l₁ substantially greater than the second variable airspace l₂ at both ends of the range. 

What is claimed is:
 1. A pancratic wide-angle objective comprising:a stationary negative front component; a stationary multilens positive rear component; and an axially movable positive intermediate component between said front and rear components; said front component being a meniscus-shaped lens member with a concave surface turned toward said intermediate component and with an absolute focal length greater than that of said rear component; said intermediate component being a biconvex lens member with a focal length greater than the absolute focal length of said front component, the absolute focal lengths of said front component, said intermediate component and said rear component having a ratio of approximately 4:5:3.
 2. An objective as defined in claim 1 wherein said front and rear components are separated by an airspace greater than the focal length of said front component.
 3. An objective as defined in claim 2 wherein said airspace equals approximately twice the focal length of said rear component.
 4. An objective as defined in claim 1 wherein the separation of said intermediate component from said front component substantially exceeds its separation from said rear component at both ends of its range of displacement.
 5. An objective as defined in claim 1 wherein said front component is a single lens L₁, said intermediate component is a signal lens L₂ and said rear component consists of a positive first lens L₃, a positive second lens L₄, a negative third lens L₅ and a positive fourth lens L₆.
 6. An objective as defined in claim 5 wherein said lenses L₁ - L₆ have thicknesses d₁ - d₆, radii r₁ - r₁₂ and separations l₁ - l₅ whose numerical values, together with their refractive indices n_(d) and Abbe numbers v_(d), are substantially as given in the following Table:

                      Thicknesses                                                                    and                                                          Lenses                                                                               Radii       Separations  n.sub.d                                                                              v.sub.d                                   ______________________________________                                               r.sub.1                                                                              +     7.072                                                        L.sub.1                 d.sub.1                                                                            0.229      1.658 50.9                                    r.sub.2                                                                              +     1.972                                                                                    5.530 f.sub.min                                                            l.sub.1                                                                            5.102 f.sub.M                                                                  4.516 f.sub.max                                          r.sub.3                                                                              +     8.596                                                        L.sub.2                 d.sub.2                                                                            0.457      1.589 61.3                                    r.sub.4                                                                              -     4.856                                                                                    0.014 f.sub.min                                                            l.sub.2                                                                            0.443 f.sub.M                                                                  1.029 f.sub.max                                          r.sub.5                                                                              +     2.137                                                        L.sub.3                 d.sub.3                                                                            0.372      1.589 61.3                                    r.sub.6                                                                              +     14.894                                                                               l.sub.3                                                                            0.014                                                    r.sub.7                                                                              +     1.425                                                        L.sub.4                 d.sub.4                                                                            0.500      1.589 61.3                                    r.sub.8     ∞                                                                              l.sub.4                                                                            0.104                                                    r.sub.9                                                                              -     5.597                                                        L.sub.5                 d.sub.5                                                                            0.643      1.785 25.8                                    r.sub.10                                                                             +     0.768                                                                                l.sub.5                                                                            0.121                                                    r.sub.11                                                                             +     4.705                                                        L.sub.6                 d.sub.6                                                                            0.286      1.691 54.7                                    r.sub.12                                                                             -     1.364                                                        ______________________________________                                    


7. An objective as defined in claim 5 wherein said lenses L₁ - L₆ have thicknesses d₁ -d₆, radii r₁ - r₁₂ and separations l₁ - l₅ whose numerical values, together with their refractive indices n_(d) and Abbe numbers v_(d), are substantially as given in the following Table:

                      Thicknesses                                                                    and                                                          Lenses                                                                               Radii       Separations  n.sub.d                                                                              v.sub.d                                   ______________________________________                                               r.sub.1                                                                              + 14.316                                                           L.sub.1               d.sub.1                                                                            0.286      1.589 61.3                                      r.sub.2                                                                              + 1.960                                                                                      5.497 f.sub.min                                                            l.sub.1                                                                            5.011 f.sub.M                                                                  4.524 f.sub.max                                            r.sub.3                                                                              + 5.234                                                            L.sub.2               d.sub.2                                                                            0.458      1.589 61.3                                      r.sub.4                                                                              - 7.490                                                                                      0.058 f.sub.min                                                            l.sub.2                                                                            0.545 f.sub.M                                                                  1.032 f.sub.max                                            r.sub.5                                                                              + 2.434                                                            L.sub.3               d.sub.3                                                                            0.344      1.589 61.3                                      r.sub.6                                                                              + 33.380                                                                                 l.sub.3                                                                            0.014                                                      r.sub.7                                                                              + 1.507                                                            L.sub.4               d.sub.4                                                                            0.558      1.589 61.3                                      r.sub.8                                                                              ∞                                                                                  l.sub.4                                                                            0.106                                                      r.sub.9                                                                              - 5.485                                                            L.sub.5               d.sub.5                                                                            0.573      1.785 26.1                                      r.sub.10                                                                             + 0.888                                                                                  l.sub.5                                                                            0.129                                                      r.sub.11                                                                             + 3.800                                                            L.sub.6               d.sub.6                                                                            0.315      1.691 54.7                                      r.sub.12                                                                             - 1.722                                                            ______________________________________                                    


8. An objective as defined in claim 5 wherein said lenses L₁ - L₆ have thicknesses d₁ - d₆, radii r₁ - r₁₂ and separations l₁ - l₅ whose numerical values, together with their refractive indices n_(d) and Abbe numbers v_(d), are substantially as given in the following Table:

                       Thicknesses                                                                    and                                                         Lenses                                                                               Radii        Separations                                                                               n.sub.d                                                                               v.sub.d                                   ______________________________________                                               r.sub.1                                                                              + 13.048                                                           L.sub.1                d.sub.1                                                                            0.255  1.589  51.4                                        r.sub.2                                                                              + 2.107                                                                                       5.452                                                                      l.sub.1                                                                            4.956                                                                          4.459                                                     r.sub.3                                                                              + 5.226                                                            L.sub.2                d.sub.2                                                                            0.454  1.589  61.3                                        r.sub.4                                                                              - 7.480                                                                                       0.050                                                                      l.sub.2                                                                            0.547                                                                          1.043                                                     r.sub.5                                                                              + 2.282                                                            L.sub.3                d.sub.3                                                                            0.369  1.589  61.3                                        r.sub.6                                                                              + 31.295                                                                                  l.sub.3                                                                            0.014                                                     r.sub.7                                                                              + 1.412                                                            L.sub.4                d.sub.4                                                                            0.496  1.589  61.3                                        r.sub.8                                                                              ∞                                                                                   l.sub.4                                                                            0.099                                                     r.sub.9                                                                              - 5.555                                                            L.sub.5                d.sub.5                                                                            0.638  1.785  26.1                                        r.sub.10                                                                             + 0.755                                                                                   l.sub.5                                                                            0.135                                                     r.sub.11                                                                             + 3.444                                                            L.sub.6                d.sub.6                                                                            0.284  1.691  54.7                                        r.sub.12                                                                             - 1.376                                                            ______________________________________                                     